Earthquake Damage to Passive Fire Protection Systems in Tall Buildings and its Impact on Fire Safety

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University of Canterbury

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Doctoral

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New Zealand is a country which is extremely prone to seismic activity. One of the many
impacts an earthquake may have is to cause fires. If a fire was to start in a damaged multistorey
structure the safety of the occupants would undoubtedly be in question.
During an earthquake large lateral forces are experienced by tall buildings, this in turn causes
deformations to take place. It is these deformations that can cause damage to various parts of
the structure. One very important component of any structure is its passive fire protection;
unfortunately passive protection systems such as Gypsum plasterboard walls are very
vulnerable to earthquake damage. Discovering the extent to which this reduces the fire safety
of buildings is the primary objective of this project.
Currently in New Zealand there are no legislative design criteria for the event of fire
following an earthquake. Another aim of this research is to gain a further understanding of
this gap between the design of tall buildings for the demands of earthquake and the demands
of fire. A greater understanding of the risks posed by post-earthquake fire is to be gained by
addressing the vulnerability of tall buildings.
To determine the level of risk associated with post-earthquake fire the topic was split into two
parts. The first part involved developing models to calculate a factor of safety for burning
buildings as a ratio of available and actual escape times. The second part looked at how
damage to plasterboard walls, protecting escape paths, would affect the fire safety of the
building. By considering the results of these two parts an overall assessment of the risk
associated with post-earthquake fire was made.
It was found that for fire following an earthquake in buildings greater than ten stories, in
which the sprinklers do not operate; the occupants may be unsafe because the expected escape
time is greater than the expected failure time of the fire rated walls surrounding the escape
route.